EDDH RWY 23 has been closed due to work in progress close to the RWY threshold for three weeks. Some routine maintenance is also being carried out. During these three weeks the unobstructed surface has been used during the HAMBURG AIRPORT CLASSICS aviation festival as an airshow runway, serving vintage airplanes and also the first glider landings at Fuhlsbüttel in around three decades. On saturday, a B747SP VIP variant that is undergoing maintenance at LH Technik sat close to the RWY 05 threshold. I don't know whether an engine test run was taking place but this happens frequently, usually at the RWY 15 threshold when RWY 05/23 is servicable.